The purpose of this study is to test the effects of nicotine on cognition with the following schizophrenia endophenotypes: prepulse inhibition, antisaccades, the continuous performance test, spatial working memory and a verbal memory task. Schizophrenia patients, unaffected first-degree relatives of schizophrenia patients and healthy controls receive transdermal nicotine in a double-blind, placebo-controlled, crossover study.